The present invention relates to a transflective liquid crystal display device, and more particularly to an IPS-type transflective liquid crystal display device.
A transflective liquid crystal display device which has a transmissive portion and a reflective portion within one sub pixel has been used as a display for a portable digital assistant.
Such a transflective liquid crystal display device adopts a vertical electric field method in which an electric field is applied to liquid crystal sandwiched between a pair of substrates in the direction perpendicular to planes of the pair of substrates thus driving the liquid crystal. Further, to make the characteristic of the transmissive portion and the reflective portion match each other, a stepped portion is provided between the transmissive portion and the reflective portion, and a phase difference plate is arranged between a polarizer and a liquid crystal layer.
As a type of liquid crystal display device, there has been known an IPS-type liquid crystal display device. In this IPS-type liquid crystal display device, pixel electrodes (PX) and counter electrodes (CT) are formed on the same substrate, and an electric field is generated between the pixel electrodes (PX) and the counter electrodes (CT) so as to rotate the liquid crystal in a plane of the substrate thus controlling a contrast. Accordingly, the IPS-type liquid crystal display device has the characteristic that the gradation of a display image is not inverted even when a screen is viewed obliquely.
To make use of this characteristic, the constitution of the transflective liquid crystal display device using the IPS-type liquid crystal display device has been proposed in JP-A-2003-344837 (patent document 1), for example.
Further, as a driving method of the IPS-type liquid crystal display device, driving of counter electrodes for every display line is described in JP-A-2001-194685 (patent document 2) and JP-A-10-31464 (patent document 3), for example.